Monte Carlo modelling of X-ray absorptiometry and its application to body composition studies

This thesis applies Monte Carlo techniques to the study of X-ray absorptiometric methods of bone mineral measurement. These studies seek to obtain information that can be used in efforts to improve the accuracy of the bone mineral measurements. A Monte Carlo computer code for X-ray photon transport at diagnostic energies has been developed from first principles. This development was undertaken as there was no readily available code which included electron binding energy corrections for incoherent scattering and one of the objectives of the project was to study the effects of inclusion of these corrections in Monte Carlo models. The code includes the main Monte Carlo program plus utilities for dealing with input data. A number of geometrical subroutines which can be used to construct complex geometries have also been written. The accuracy of the Monte Carlo code has been evaluated against the predictions of theory and the results of experiments. The results show a high correlation with theoretical predictions. In comparisons of model results with those of direct experimental measurements, agreement to within the model and experimental variances is obtained. The code is an accurate and valid modelling tool. A study of the significance of inclusion of electron binding energy corrections for incoherent scatter in the Monte Carlo code has been made. The results show this significance to be very dependent upon the type of application. The most significant effect is a reduction of low angle scatter flux for high atomic number scatterers. To effectively apply the Monte Carlo code to the study of bone mineral density measurement by photon absorptiometry the results must be considered in the context of a theoretical framework for the extraction of energy dependent information from planar X-ray beams. Such a theoretical framework is developed and the two-dimensional nature of tissue decomposition based on attenuation measurements alone is explained. This theoretical framework forms the basis for analytical models of bone mineral measurement by dual energy X-ray photon absorptiometry techniques. Monte Carlo models of dual energy X-ray absorptiometry (DEXA) have been established. These models have been used to study the contribution of scattered radiation to the measurements. It has been demonstrated that the measurement geometry has a significant effect upon the scatter contribution to the detected signal. For the geometry of the models studied in this work the scatter has no significant effect upon the results of the measurements. The model has also been used to study a proposed technique which involves dual energy X-ray transmission measurements plus a linear measurement of the distance along the ray path. This is designated as the DPA( +) technique. The addition of the linear measurement enables the tissue decomposition to be extended to three components. Bone mineral, fat and lean soft tissue are the components considered here. The results of the model demonstrate that the measurement of bone mineral using this technique is stable over a wide range of soft tissue compositions and hence would indicate the potential to overcome a major problem of the two component DEXA technique. However, the results also show that the accuracy of the DPA( +) technique is highly dependent upon the composition of the non-mineral components of bone and has poorer precision (approximately twice the coefficient of variation) than the standard DEXA measurements. These factors may limit the usefulness of the technique. These studies illustrate the value of Monte Carlo computer modelling of quantitative X-ray measurement techniques. The Monte Carlo models of bone densitometry measurement have:- 1. demonstrated the significant effects of the measurement geometry upon the contribution of scattered radiation to the measurements, 2. demonstrated that the statistical precision of the proposed DPA( +) three tissue component technique is poorer than that of the standard DEXA two tissue component technique, 3. demonstrated that the proposed DPA(+) technique has difficulty providing accurate simultaneous measurement of body composition in terms of a three component model of fat, lean soft tissue and bone mineral,4. and provided a knowledge base for input to decisions about development (or otherwise) of a physical prototype DPA( +) imaging system. The Monte Carlo computer code, data, utilities and associated models represent a set of significant, accurate and valid modelling tools for quantitative studies of physical problems in the fields of diagnostic radiology and radiography.

Torsional Interaction Studies on a Power System Compensated by SSSC and Fixed Capacitor

In this paper, a static synchronous series compensator (SSSC), along with a fixed capacitor, is used to avoid torsional mode instability in a series compensated transmission system. A 48-step harmonic neutralized inverter is used for the realization of the SSSC. The system under consideration is the IEEE first benchmark model on SSR analysis. The system stability is studied both through eigenvalue analysis and EMTDC/PSCAD simulation studies. It is shown that the combination of the SSSC and the fixed capacitor improves the synchronizing power coefficient. The presence of the fixed capacitor ensures increased damping of small signal oscillations. At higher levels of fixed capacitor compensation, a damping controller is required to stabilize the torsional modes of SSR.

Getting that piece of paper : mental health nurses' experience of undertaking doctoral studies in Victoria, Australia

The aim of this study was to explore the experience of mental health nurses undertaking doctoral studies. The study was conducted in Victoria, Australia. A descriptive exploratory approach to inquiry was used for this study. Participants were mental health nurses who had successfully completed a doctoral qualification. Eligibility for inclusion required participants to be residing in Victoria (irrespective of where their doctoral studies were undertaken) and to have conducted their research within the domain of mental health and/or currently employed in the field of mental health nursing. Of the 20 potential participants invited, 16 accepted the invitation. Five emergent themes were explicated from narrative analyses. These themes were being a trail blazer, positioning for professional advancement, achieving a balance between competing priorities, maintaining a commitment to the development of the profession, and a point of affirmation. An understanding of the experience of undertaking doctoral studies can be used to influence the development of strategies to encourage more mental health nurses to consider undertaking a doctoral degree.

Fuzzy logic power system stabilizer in multimachine stability studies

Power system stabilizers (PSS) work well at the particular network configuration and steady state conditions for which they were designed. Once conditions change, their performance degrades. This can be overcome by an intelligent nonlinear PSS based on fuzzy logic. Such a fuzzy logic power system stabilizer (FLPSS) is developed, using speed and power deviation as inputs, and provides an auxiliary signal for the excitation system of a synchronous motor in a multimachine power system environment. The FLPSS's effect on the system damping is then compared with a conventional power system stabilizer's (CPSS) effect on the system. The results demonstrate an improved system performance with the FLPSS and also that the FLPSS is robust

A framework for strategic infrastructure asset management

The concept of asset management is not a new but an evolving idea that has been attracting attention of many organisations operating and/or owning some kind of infrastructure assets. The term asset management have been used widely with fundamental differences in interpretation and usage. Regardless of the context of the usage of the term, asset management implies the process of optimising return by scrutinising performance and making key strategic decisions throughout all phases of an assets lifecycle (Sarfi and Tao, 2004). Hence, asset management is a philosophy and discipline through which organisations are enabled to more effectively deploy their resources to provide higher levels of customer service and reliability while balancing financial objectives. In Australia, asset management made its way into the public works in 1993 when the Australian Accounting Standard Board issued the Australian Accounting Standard 27 – AAS27. Standard AAS27 required government agencies to capitalise and depreciate assets rather than expense them against earnings. This development has indirectly forced organisations managing infrastructure assets to consider the useful life and cost effectiveness of asset investments. The Australian State Treasuries and the Australian National Audit Office was the first organisation to formalise the concepts and principles of asset management in Australia in which they defined asset management as “ a systematic, structured process covering the whole life of an asset”(Australian National Audit Office, 1996). This initiative led other Government bodies and industry sectors to develop, refine and apply the concept of asset management in the management of their respective infrastructure assets. Hence, it can be argued that the concept of asset management has emerged as a separate and recognised field of management during the late 1990s. In comparison to other disciplines such as construction, facilities, maintenance, project management, economics, finance, to name a few, asset management is a relatively new discipline and is clearly a contemporary topic. The primary contributors to the literature in asset management are largely government organisations and industry practitioners. These contributions take the form of guidelines and reports on the best practice of asset management. More recently, some of these best practices have been made to become a standard such as the PAS 55 (IAM, 2004, IAM, 2008b) in UK. As such, current literature in this field tends to lack well-grounded theories. To-date, while receiving relatively more interest and attention from empirical researchers, the advancement of this field, particularly in terms of the volume of academic and theoretical development is at best moderate. A plausible reason for the lack of advancement is that many researchers and practitioners are still unaware of, or unimpressed by, the contribution that asset management can make to the performance of infrastructure asset. This paper seeks to explore the practices of organisations that manage infrastructure assets to develop a framework of strategic infrastructure asset management processes. It will begin by examining the development of asset management. This is followed by the discussion on the method to be adopted for this paper. Next, is the discussion of the result form case studies. It first describes the goals of infrastructure asset management and how they can support the broader business goals. Following this, a set of core processes that can support the achievement of business goals are provided. These core processes are synthesised based on the practices of asset managers in the case study organisations.

Aboriginal community control and decolonizing health policy : a yarn from Australia

This chapter outlines: a brief history of Australian Aboriginal health and health policy and then moves on to demonstrate how the Victorian Aboriginal Community Controlled Health Organisation (VACCHO) undertakes its work and is an example of 'decolonizing policy in action'. Moreover, it highlights how Aboriginal participation in the development of policy and in the planning, delivery, management and evaluation of health programs enables policies and programs to respond effectively to the needs of Aboriginal people and to change future health outcomes for them. It showcases how Aboriginal decision-making has gone some way to decolonizing policymaking and has addressed the power imbalance - both of which have been critical in the improvement in Aboriginal health outcomes.

Aboriginal public health and education : has it made a difference in practice?

Over the years, public health in relation to Australian Aboriginal people has involved many individuals and groups including health professionals, governments, politicians, special interest groups and corporate organisations. Since colonisation commenced until the1980s, public health relating to Aboriginal and Torres Strait Islander people was not necessarily in the best interests of Aboriginal and Torres Strait Islander people, but rather in the interests of the non-Aboriginal population. The attention that was paid focussed more generally around the subject of reproduction and issues of prostitution, exploitation, abuse and venereal diseases (Kidd, 1997). Since the late 1980s there has been a shift in the broader public health agenda (see Baum, 1998) along with public health in relation to Aboriginal and Torres Strait Islander people (NHMRC, 2003). This has been coupled with increasing calls to develop appropriate tertiary curriculum and to educate, train, and employ more Aboriginal and Torres Strait Islander and non-Aboriginal people in public health (Anderson et al., 2004; Genat, 2007; PHERP, 2008a, 2008b). Aboriginal and Torres Strait Islander people have been engaged in public health in ways in which they are in a position to influence the public health agenda (Anderson 2004; 2008; Anderson et al., 2004; NATSIHC, 2003). There have been numerous projects, programs and strategies that have sought to develop the Aboriginal and Torres Strait Islander Public Health workforce (AHMAC, 2002; Oldenburg et al., 2005; SCATSIH, 2002). In recent times the Aboriginal community controlled health sector has joined forces with other peak bodies and governments to find solutions and strategies to improve the health outcomes of Aboriginal and Torres Strait Islander peoples (NACCHO & Oxfam, 2007). This case study chapter will not address these broader activities. Instead it will explore the activities and roles of staff within the Public Health and Research Unit (PHRU) at the Victorian Aboriginal Community Controlled Health Organisation (VACCHO). It will focus on their experiences with education institutions, their work in public health and their thoughts on gaps and where improvements can be made in public health, research and education. What will be demonstrated is the diversity of education qualifications and experience. What will also be reflected is how people work within public health on a daily basis to enact change for equity in health and contribute to the improvement of future health outcomes of the Victorian Aboriginal community.